1994 e320 high idle
 

I have a 1994 e320, I had a problem with the idling, it used to rev up and down.... i changed the spark plugs, wires, mass air flow sensor, some vaccuum lines. but now the idle stays high. i tried adjusting it, but it stays the same. in drive its at about 800, and in park it settle at about 1200 or 1300.
it used to be in drive around 500 and park 700.

I read the codes i got:

code 6 in the built in reader
code 8 in pin 8
code 2 in pin 14

any ideas?

I would like to add that during this problem i did play around with the cables adjustments in the engine compartment and at the gas pedal.

SEND me your vin and email so I can send you some documents. I have some good info on your problem ))

wdbea32e1rc114533
lebstyle@hotmail.com
thanks

Have your "throttle actuator" checked.

Check out MENU#24 on my pages for the "ETA" problem. . . those codes point to a failing ETA . . . . or a bad wiring harness. If the W/H hasn't been changed you probably should start there.

i have chekced all the wiring , it is still good. i think the throttle actuator is working properly. b/c i know its working. if it wasnt, the car would be idling up and down. im thinking it something else triggering that.

Check that the cable has a 1/4 slack and that the rug is not bunched up. Both of those will throw Closed Throttle Position code..
also check that the cable is not sticking..

what do u mean by the rug bunched up.

Check around the base of the gas pedal.. See them get extra mats and rugs , along with dirt and sand, etc..that stops the CTP sw from getting closed, just like the throtle cable can..

Does your cruise control work?

This is from a thread I started about a year ago..........


Update: the rest of the story.....

Problem is back, below is description of problem.

Installed rebuilt unit in a 1995 E320 Sedan.
Initially the unit operated correctly, 2 days later, operation became
intermittent. Symptoms are intermittent high idle speed (1400 RPM in park,
1000 RPM in gear) and inoperative cruise control. (either both symptoms are
present, or neither are present. never one without the other) Shutting off
the car and restarting will sometimes cure both problems, but they both
reoccur. Retrieval of stored fault codes (via impulse code reader, not HHT)
consistently yields the following:

Diagnostic module: code 6: Idle speed control inoperative

ECU module: code 8: Idle speed control (ISC) system at upper or lower
control stop

HFM SFI module: code 2: EA/CC/ISC control module (N4/1) or Safety contact
switch (M16/1s1) or Stop lamp
switch or Cruise control switch or Actual value potentiometer or Starter
lock-out/back-up
lamp switch or engine speed signal or vehicle speed signal or closed
throttle position
switch or safety relay in EA/CC/ISC control module

Out of desperation, I replaced the remanufactured unit with a known working
unit pulled from an identical fully functional vehicle. Idle speed/cruise
control now work properly. So far, there is no indication of intermittent
failure.

Returned unit to Beckmann for testing, they confirmed reman unit was defective. (the drive motor was bad)

Hope this story helps someone else........................

Reman . . what??? ETA??

What ECU module???

Tnx for posting that . . .all info is good info.

A suggestion to DTC posters is to use the NAME of the module being read from the PIN. . . . not just the pin. The reason is simple: In a E320 the diag connector's pin layout is different from that of a S500; 16 vs 38 pins. By talking "function", all confustion is eliminated.

I have been noticing also hard shifting in the transmission, and it shifts quickly. you can feel it shift a gear right before you stop.
i am thinking possibly a vaccuum leak might cause it?
i checked the cable, it is pretty free.

I just had a similar issue on my own car (94' E320). The throttle return spring was broken. ;)

where is that located? and what does it look like?
thanks

one thing I have been noticing also is that it feels like a slight backfire when i am driving at low speeds, and its been spending alot of gas. and shifting hard at times.
any ideas?
thanks

Sorry Jim, After rereading my post, I can see where I left room for confusion.

The "unit" I refer to is indeed the throttle actuator. The ECU module I refer to is pin #8, HFM/SFI module. (I keep a printout of a thread from cdanschwartz with all the DTC's listed. The printout refers to pin 8 as "ECU"--probably should be "HFM/SFI")

When I originally went through all this about a year ago, I was (and still am) very much in a learning mode........

Lebstyle:

The throttle return spring is located on the aft side of the throttle actuator. It is accessible by removing the black air cross over tube, the rubber air tube that sits on top of the throttle actuator, and the variable intake valve that sits in the middle of the black plastic intake manifold. To remove the variable intake valve you have to remove the four rubber plugs to expose four allen head bolts.....

By the way, does your cruise control work?

Just recognised another mistake--the HFM/SFI fault I referred to was actually a CC/ETA fault. My fault descriptions are all correct, but I had the modules labled incorrectly. Jim: thanks for pointing this out.

For clarification, here is what I had with all the correct labling:

Diagnostic module via built in reader: code 6: Idle speed control inoperative

Pin 8, (HFM/SFI): code 8: Idle speed control (ISC) system at upper or lower
control stop

Pin 14, (ETA/CC/ISC): code 2: ETA/CC/ISC control module (N4/1) or Safety contact
switch (M16/1s1) or Stop lamp
switch or Cruise control switch or Actual value potentiometer or Starter
lock-out/back-up
lamp switch or engine speed signal or vehicle speed signal or closed
throttle position
switch or safety relay in EA/CC/ISC control module

Tnx for clarifying your post; it didn't read 'right'. . . Pin 14 is "EA" module standing for "Electronic Accelerator" . . .

This is the first case that I know where the CC went bad in the EA module but if it can happen, it's worth posting it.

i have'nt checked my cruise if it works, but i will today.
whats the best way to check for a vacuum leak?

i tried the cruise while the CE light was on today, it didnt seem to be working

I suspect you have a bad throttle actuator. If this were my car, I would contact Beckmann Technologies or 4Mercedes to see about a remanufactured unit. Best way is to send yours in for testing/remanufacturing. That way you verify it is indeed bad prior to spending lots of $$$. If you can't do without the car for a week or so, either Beckmann or 4Mercedes can send you a rebuilt unit--they will add a core charge which will be refunded when they receive your old unit. When I went through this about a year ago, 4 Mercedes was about $500.00, Beckmann was about $675.00. I used Beckmann, because they were much more helpful and professional.

J. M. van Swaay

I agree with JM's recomendation of Beckmann. They 'know' ETAs and can properly test to determine if it is bad.

Received a email regarding an ETA repair done by "4Mercedes". Great horror story that you wouldn't believe. Asked him to post it here but he's having trouble making a 'post'. So all I can say is I wouldn't recommend them . . . price is less but . . . :behead:

how can i find the N4/1 module on my car, 94 e320
thanks

the reason for my question is that I played around alot with the accelerator pedal adjustment, that i might have messed something up to make my car idle high in drive and park slightly, it will not go any lower under any circumstances, and gives me the code 6
pin 8 code 8
pin 14 code 2

but other than that the car runs perfect.

Email Sent

can the co potentiometer be adjusted on my car?
94 e320

Most likely yes but I could be wrong Ill look later.

b/c the car idle is a little too high, i can live with that, but its spending alot of gas. but it runs smooth.

It has a LH-SFI (hot wire) closed loop system controlling Lamba. See MENU#4 for how-it-works. There's no adjustment that I know of . . .

No Hot Wire on that chassis.
They are HFM/SFI.

ill look but if I remember right the potentimeter cant be adjusted on hfm systems. Its an electrical device. The only thing you can adjust is the mixture and a few other things. You could try cleaning the fuel injectors and replacing the air filter to start addressing the gas problem. How many miles to the gallon are you supposed to get on the highway and city?
I know mercedes arent known for good gas mileage. Think one of the s class gets like 10 to 15 miles to the gallon.

I changed all that already. the idle stays steady, about 800 on drive, and 1200 on park. im only getting like 13 miles per gallon now.
i think its running too rich.

You gotta a lambda tester? You are going to need a need lambda tester to see what the percantage is. 50% is nothing wrong, anything lower or higher than that means you got problems. check your spark plugs and see what color they are. If they are black then its running rich.

and what do i do if its running rich?

Check the Purge Switchover Valve (Y58/1) on the left side of engine compartment close to ABS unit.
Check EGR valve also if you got one European cars does not have EGR valve,

ok will do, i know how to check the egr, but the purge switch over valve, im not sure how to check it.
thanks

I would just use a lambda tester and see what perctange its at. You need to get the car up to operating temperature and measure the perctange. I wouldnt replace this part or that part until you get a lambda read out. You could be wasting money and replacing parts you dont need to.

The first check for rich condition on 104 w/HFM is fuel pressure regulator.
They are a common fault item for leaking.
Take the vac lline OFF and look/smell for fuel in the line ..There should be NONE.
If there is , replace the regulator.
What happens w/bad reg. is un-metered fuel gets sucked into the engine intake through the vac line of the regulator..............
That will effect BOTH fuel/air mixture and idle speed.
This test takes 4.9 nano secs. to do, so that is why it should be First Check

i checked the fuel pressure reg air line, and i did smell gas in there.
one thing i have been noticing is that when i first start it, the idle is low, about 600, then a few seconds later, it goes up.
but it does stay low for a bit.

how do u change that by the way, does it just pull out?
thanks

to change the fuel pressure regulator make all disconnects and it should come out.

Do you know there is all this info in the Archieves and this site has an excellent Search Feature with an extensive Library ?

Sometimes I back off to answer b/c I know after I send you in the right direction , I am going to get back 5 questions like "Where is that?? " or "
"What does it look like ?"
Use that search engine. ..this simple stuff all been covered here a zillion times.

I removed the fuel pressure regulator.
I didnt release any pressure before i took it out, so when i took the pin out, it shot right out with a bang, im not sure if there was just too much pressure in there. specially when the car was off for a few hours.

i put air pressure in from the bottom, and nothing came out where the vacuum line connects.

does it seem like its bad?
thanks

i was also reading some threads and someons had a similar problem but with a higher rpm. turned out it was the ovp relay.
but as i mentined before, when i released the pin on the pressure regulator, it shot up and the gas hit me in the face with a bang.
thanks

I forgot to mention when working with any component in the fuel system ie fuel pump etc depressurize the system or gas will spray in your face. I thought you would automically depressurize the system since it seemed pretty obivous.

but is the gas system supposed to hold that much pressure even when the car has been off for a while?

When you shut the car off not all the unused gas in the system goes to the tank some of it stays in the fuel system in the engine compartment as you found out today. My 190E that doesnt run at all, had some fuel still in the pressure regular and at the eha unit even though the car hasnt ran in a while when I removed them.

>>but as i mentined before, when i released the pin on the pressure regulator, it shot up and the gas hit me in the face with a bang.
>>

What did you take the regulator off for ??
The test for reg is done on the car. The test I mentioned is for a reg leaking diapragm.

If you pass that test, then you do a Fuel Pressure test..this will test the pump/s and the regulator for spec.

Car at idle with vac hose to reg connected:
3.2-3.6 Bar
At idle, vac hose disconnected :
3.7-4.2 Bar
System pressure after at least 30 min wait :
No less than 2.5 Bar.

All these specs are taken right at the test port valve on the fuel Rail..you do not take the Reg off for any of these test [ uncluding the other quick test I gave you]
..but , if you do have to remove a reg, you of course release the system pressure at the test port valve....and turning the engine off too would be a good idea.. :)
If the pressure is too high , then the reg is not doing it's job and that will cause the rich condition. This can aslo be caused by a vac leak on the vac line that controls the regulator.
This HFM system is full electronic, so the Fuel Pressure HAS to be to spec.